This project aims to study the effects of air particulate matter on HDL function and atherosclerosis. Air pollution has been associated with significant adverse health effects leading to increased morbidity and mortality. Cumulative epidemiological and experimental data have shown that exposure to air pollutants lead to increased cardiovascular ischemic events and enhanced atherosclerosis. It appears that these associations are much stronger with the air particulate matter (PM) component and that the smaller particles are the most pathogenic. We have found that ultrafine particles (<0.18 5m) preferentially promote atherosclerosis, partly due to their high content in redox cycling chemicals and their ability to synergize with known proatherogenic mediators in the promotion of systemic tissue oxidative stress and proinflammatory effects. Indeed, we have recently reported that diesel exhaust particles, highly enriched in ultrafines, synergize with oxidized phospholipids in the induction of a large number of genes in human microvascular endothelial cells, many of which belong to antioxidant (e.g. heme oxygenase-1), proinflammatory, unfolded protein response or proapoptotic pathways of relevance in vascular inflammatory processes. These systemic effects result in the generation of dysfunctional HDL, which loses its antiinflammatory capacity or even becomes proinflammatory, despite the upregulation of antioxidant genes, an important line of defense to protect against PM toxicity. We hypothesize that exposure to ambient PM result in dysfunctional HDL and enhanced atherosclerosis via the induction of systemic prooxidant and proinflammatory effects and that a decreased antioxidant response will significantly enhance the degree of HDL dysfunction and development of atherosclerosis. We propose the following three specific aims to test our hypothesis: 1) to characterize the nature of HDL changes induced by the exposure to air particulate matter. We will use diesel exhaust as a model air pollutant to determine toxicological parameters such as effective dose and kinetics involved in the induction of HDL dysfunction. Plasma HDL will be the subject of an extensive functional and structural characterization that will include proteomic and lipidomic approaches; 2) to determine the effects of decreased antioxidant response in the protection against air pollutant proinflammatory effects and atherosclerosis. We will use conditional heme oxygenase-1 KO mice in endothelial cells and macrophages to study the effect of HO-1 ablation and impaired protection against oxidative stress in a tissue-specific manner, on the degree of PM- induced HDL dysfunction and atherosclerosis; 3) to evaluate the relationship between air particulate matter and human HDL dysfunction by studying whether experimental exposures to concentrated ambient particles lead to alteration in HDL antiinflammatory and antioxidant functions. This research project represents a logical extension of the candidate's previous research and thanks to the high level of institutional support given by UCLA; it will be extremely valuable to establish him as an independent investigator in the environmental field.